Filters

ABSTRACT

A filter comprising: a filter cartridge ( 161 ) and a housing having at least one fitting ( 15   a, b, c ) and defining a chamber, the filter cartridge being disposed in the chamber, wherein the housing includes a fluid conduit ( 164 ) which extends axially from the fitting ( 15   a ) along the periphery of the filter cartridge chamber, the fluid conduit being isolated from the filter cartridge chamber along a substantial portion of the length of the fluid conduit.

[0001] This application claims priority based on U.S. ProvisionalApplication No. 60/203,948, filed May 12, 2000 and U.S. ProvisionalApplication No. 60/216,697, filed Jul. 7, 2000, both of which areincorporated by reference.

TECHNICAL FIELD

[0002] The present invention relates to filters which may be used in awide variety of applications including, for example, the filtration of aphoto-resist liquid.

BACKGROUND OF THE INVENTION

[0003] Many fluids, such as photo-resist liquids used in themicro-electronics industry, are exceedingly expensive. These liquidsmust be filtered immediately prior to being used or impurities in theliquids can damage the micro-electronic components being fabricated.

[0004] Conventional filters have many problems associated with them. Forexample, many conventional filters have relatively large volumes withinthem, e.g., hold up volumes, which collect and trap the liquid. Thesehold up volumes are expensive because the expensive liquid trapped inthe hold up volumes is discarded when the filter is discarded. Further,many of these filters have dead zones where the flow of fluid stagnates.When a liquid such as a photo-resist liquid stagnates it can undergochemical and/or physical changes which can be detrimental to thefabrication process. In addition, when the liquid is first pumpedthrough a filter having large hold up volumes and dead zones, the amountof time and the amount of wasted liquid required to fill the hold upvolumes and the dead zones before a clean filtered liquid emerges fromthe outlet of the filter can be considerable.

SUMMARY OF THE INVENTION

[0005] The present invention overcomes many problems associated withconvention filters, including one or more of the problems previouslydescribed.

[0006] In accordance with one aspect of the invention, a filtercomprises a filter cartridge and a housing. The housing has at least onefitting and defines a chamber, and the filter cartridge is disposed inthe chamber. The housing further includes a fluid conduit which extendsaxially from the fitting along the periphery of the filter cartridgechamber. The fluid conduit is isolated from the filter cartridge chamberalong a substantial portion of the length of the fluid conduit.

[0007] In accordance with another aspect of the invention, a filtercomprises a filter cartridge having an end cap, and a housing having atleast one fitting and defining the chamber. The filter cartridge isdisposed in the chamber with the end cap of the filter cartridgeadjacent to a wall of the housing. The housing further includes a radialpassage which extends along the end cap of the filter cartridge or thewall of the housing or both the end cap and the housing wall. The radialpassage fluidly communicates between the fitting and the filtercartridge chamber.

[0008] In accordance with another aspect of the invention, a filtercomprises a filter cartridge, a housing, and a keying mechanism. Thehousing defines a chamber and the filter cartridge is disposed in thechamber. The keying mechanism is cooperatively arranged with the housingand the filter cartridge to center the filter cartridge in the filtercartridge chamber.

[0009] In accordance with another aspect of the invention, a filtercomprises a filter cartridge and a housing. The filter cartridgeincludes a filter element having non-radially extending pleats. Theheight of each pleat is greater than (D−d)/2 and is less than or equalto (D²−d²)/[4(d+2t)], where D and d are the outside and insidediameters, respectively, of the pleated filter element at the crests androots of the pleats and t is the thickness of a pleat leg. The housingis fitted around the filter cartridge and has an inlet and an outletdefining a fluid flow path. The filter cartridge is disposed in thehousing in the fluid flow path and the housing and the filter cartridgeare arranged to reduce hold up volume and dead zones in the fluid flowpath.

DESCRIPTION OF THE DRAWINGS

[0010]FIG. 1 is a front view of a filtration system showing a manifoldand a capsule filter disengaged.

[0011]FIG. 2 is a side view of the filtration system of FIG. 1.

[0012]FIG. 3 is a top view of the filtration system of FIG. 1.

[0013]FIG. 4 is a front view of the filtration system of FIG. 1 showingthe manifold and the capsule filter engaged.

[0014]FIG. 5 is a partially sectioned top view of an alternative baseassembly of the filtration system of FIG. 1.

[0015]FIG. 6 is a partially sectioned side view of the base assembly ofFIG. 5 and a capsule filter mounted on the base assembly.

[0016]FIG. 7 is a partially sectioned top view of an alternative baseassembly of the filtration system of FIG. 1.

[0017]FIG. 8 is a side view of an alternative filtration system.

[0018]FIG. 9 is a partially sectioned front view of the filtrationsystem of FIG. 8.

[0019]FIG. 10 is a top view of the filtration system of FIG. 8.

[0020]FIG. 11 is a rear view of an upper portion of the filtrationsystem of FIG. 8.

[0021]FIG. 12 is a partially cutaway rear view of an upper portion ofthe filtration system of FIG. 8.

[0022]FIG. 13 is a top view of the manifold of the filtration system ofFIG. 8.

[0023]FIG. 14 is a partially cutaway side view of an alternativemounting mechanism.

[0024]FIG. 15 is a top view of the mounting mechanism of FIG. 14.

[0025]FIG. 16 is a partially cutaway side view of an alternativemounting mechanism.

[0026]FIG. 17 is a top view of the mounting mechanism of the FIG. 16.

[0027]FIG. 18 is a partially cutaway side view of an alternativemounting mechanism.

[0028]FIG. 19 is a side view of the rotatable head of the mountingmechanism of FIG. 18.

[0029]FIG. 20 is a top view of the mounting mechanism of FIG. 18.

[0030]FIG. 21 is a partially cutaway side view of a centering mechanism.

[0031]FIG. 22 is a sectional side view of an alternative centeringmechanism.

[0032]FIG. 23 is a partially cutaway top view of a portion of thecentering mechanism of FIG. 22.

[0033]FIG. 24 is a front view of a filtration system having analternative disengagement mechanism showing a manifold and a capsulefilter disengaged.

[0034]FIG. 25 is a front view of the filtration system of FIG. 24showing the manifold and the capsule filter engaged.

[0035]FIG. 26 is a sectional view of a nozzle/receptacle arrangementshowing the nozzle and the receptacle disengaged.

[0036]FIG. 27 is a sectional view of the nozzle/receptacle arrangementof FIG. 26 showing the nozzle and receptacle engaged.

[0037]FIG. 28 is a sectional view of an alternative nozzle/receptaclearrangement showing the nozzle and the receptacle disengaged.

[0038]FIG. 29 is a sectional view of the nozzle/receptacle arrangementof FIG. 28 showing the nozzle and the receptacle engaged.

[0039]FIG. 30 is a sectional view of a nozzle/receptacle arrangementshowing the nozzle and the receptacle disengaged.

[0040]FIG. 31 is a sectional view of the nozzle/receptacle arrangementof FIG. 30 showing the nozzle and the receptacle engaged.

[0041]FIG. 32 is a sectional view of a nozzle/receptacle arrangementshowing the nozzle and receptacle disengaged.

[0042]FIG. 33 is a sectional view of the nozzle/receptacle arrangementof FIG. 32 showing the nozzle and receptacle engaged.

[0043]FIG. 34 is a sectional view of a nozzle/receptacle arrangementshowing the nozzle and the receptacle disengage.

[0044]FIG. 35 is a sectional view of the nozzle/receptacle arrangementof FIG. 34 showing the nozzle and the receptacle engaged.

[0045]FIG. 36 is a sectional view of a nozzle/receptacle arrangementshowing the nozzle and the receptacle disengaged.

[0046]FIG. 37 is a sectional view of the nozzle/receptacle arrangementof FIG. 36 showing the nozzle and the receptacle engaged.

[0047]FIG. 38 is a sectional view of an alternative nozzle/receptaclearrangement.

[0048]FIG. 39 is a sectional view of an alternative nozzle/receptaclearrangement.

[0049]FIG. 40 is a sectional view of an alternative nozzle/receptaclearrangement.

[0050]FIG. 41 is a sectional view of an alternative nozzle/receptaclearrangement.

[0051]FIG. 42 is a side view of the capsule filter.

[0052]FIG. 43 is a rear view of the capsule filter of FIG. 42.

[0053]FIG. 44 is a top view of the capsule filter of FIG. 42.

[0054]FIG. 45 is a sectional side view of the capsule filter of FIG. 42.

[0055]FIG. 46 is a side view of a filter cartridge of the capsule filterof FIG. 45.

[0056]FIG. 47 is a sectional side view of an alternative capsule filter.

[0057]FIG. 48 is a sectional side view of an alternative capsule filter.

[0058]FIG. 49 is a sectional side view of an alternative bowl of acapsule filter.

[0059]FIG. 50 is atop view of the bowl of FIG. 49.

[0060]FIG. 51 is a sectional side view of an alternative bowl.

[0061]FIG. 52 is a top view of the bowl of FIG. 51.

[0062]FIG. 53 is a sectional side view of an alternative capsule filter.

[0063]FIG. 54 is a sectional side view of alternative fittings for acapsule filter.

[0064]FIG. 55 is a sectional side view of an alternative capsule filter.

[0065]FIG. 56 is a sectional side view of an alternative capsule filter.

[0066]FIG. 57 is a sectional side view of an alternative capsule filterfor use with the filtration system of FIG. 8.

[0067]FIG. 58 is a top view of the capsule filter of FIG. 57.

[0068]FIG. 59 is a sectional side view of an alternative capsule filter.

[0069]FIG. 60 is a bottom view of the capsule filter of FIG. 59.

[0070]FIG. 61 is a sectional side view of an alternative capsule filter.

[0071]FIG. 62 is a bottom view of the capsule filter of FIG. 61.

[0072]FIG. 63 is a top view of an alternative capsule filter.

[0073]FIG. 64 is a test system.

[0074]FIG. 65 is a first filter used in the test system of FIG. 64.

[0075]FIG. 66 is a bowl used for the first filter of FIG. 65.

[0076]FIG. 67 is a second filter used in the test system of FIG. 64.

[0077]FIG. 68 is a bowl used for the second filter of FIG. 67.

[0078]FIG. 69 is a third filter used in the test system of FIG. 64.

[0079]FIG. 70 is a graph of raw data.

[0080]FIG. 71 shows trends for the dispense weight [W, W′] as a functionof the shot number for the first filter.

[0081]FIG. 72 shows trends for the dispense weight [W, W′] as a functionof shot number for the third filter.

[0082]FIG. 73 shows differences of dispense weight [W, W′] between thedispense weights [W(n), W′(n′)] and weights at each saturation point[W1, W2] as a function of shot number for the first filter.

[0083]FIG. 74 shows differences of dispense weight [W, W′] between thedispense weights [W(n), W′(n′)] and weights at each saturation point[W1, W2] as a function of shot number for the second filter.

[0084]FIG. 75 shows differences of dispense weight [W, W′] between thedispense weights [W(n), W′(n′)] and weights at each saturation point[W1, W2] as a function of shot number for the third filter.

[0085]FIG. 76 shows another test system.

[0086]FIG. 77 shows the bubble and particle counts on the downstreamside of test filters in the test system of FIG. 76.

DESCRIPTION OF EMBODIMENTS

[0087] One example of a filtration system 10 is shown in FIGS. 1-4. Thefiltration system 10 generally comprises a loading/unloading equipment,e.g., a carriage 11, and further comprises a manifold 12 and a filter,such as a capsule filter 13, embodying the invention. The capsule filterincludes a filter medium, and the manifold 12 and the capsule filter 13may include mating fittings 14, 15, e.g., inlet fittings 14 a, 15 a,outlet fittings 14 b, 15 b, and vent fittings 14 c, 15 c. The carriage11 supports the capsule filter 13 and is cooperatively arranged with themanifold 12 to mount the capsule filter 13 to the manifold 12 and engagethe fittings 15 of the capsule filter 13 with the respective fittings 14of the manifold 12. For example, a mounting mechanism 16 may be arrangedbetween the carriage 11 and the manifold 12 to move the capsule filter13, e.g., longitudinally, between a disengaged position, as shown inFIGS. 1 and 2, and an engaged position, as shown in FIG. 4. In thedisengaged position, the capsule filter 13 may rest in the carriage 11and may be spaced from the manifold 12. In the engaged position, thecapsule filter 13 engages the manifold 12, and the fittings 14, 15 ofthe manifold 12 and the capsule filter 13 are sealed to one another.

[0088] With the fittings 14, 15 engaged, a pump 17, which may be fluidlycoupled and even directly attached to the manifold 12, pumps fluid,e.g., a liquid such as a liquid photo resist, into an inlet conduit inthe manifold 12, through the inlet fittings 14 a, 15 a, and into thecapsule filter 13. Gases, such as air contained in the capsule filter 13or gas bubbles entrained in the liquid, may be vented from the capsulefilter 13 via the vent fittings 14 c, 15 c and a vent conduit 20 of themanifold 12. Filtered liquid is forced by the pump through the filtermedium of the capsule filter 13 and out of the capsule filter 13 via theoutlet fittings 14 b, 15 b and an outlet conduit 21 of the manifold 12.

[0089] Once the filter medium of the capsule filter 13 becomessufficiently fouled, the pump 17 may be deactivated and the carriage 11may be moved, e.g., lowered, by the mounting mechanism 16 to thedisengaged position. A disengagement mechanism 22 may be coupled betweenthe capsule filter 13 and the carriage 11 and/or the manifold 12 todisengage the fittings 15 of the filter capsule 13 from the fittings 14of the manifold 12 as the carriage 11 is lowered. Alternatively, thecapsule filter 13 may be disengaged from the manifold 12 manually. Theold capsule filter 13 may then be replaced with a new capsule filter 13;the carriage 11 may be moved, e.g., raised, by the mounting mechanism 16to the engaged position engaging the new capsule 13 with the manifold12; and the pump 17 may then be reactivated.

[0090] The carriage 11 may be configured in a wide variety of ways. Inmay preferred embodiments, the carriage 11 may be arranged to move thecapsule filter 13, both into and out of engagement with the manifold 12,in a direction parallel to the axes of the engaged fittings 14, 15. Morepreferably the carriage 11 moves the capsule filter 13 in a directionparallel to the axes of the engaged fittings 14, 15 along most of, evenmore preferably, substantially all of, the distance that the capsulefilter 13 travels on the carriage 11. This reduces stress on thefittings 14, 15 and enhances the amount of contact and the seal betweenthe fittings.

[0091] In one example, shown in FIGS. 1 and 2, the carriage 11 mayinclude a base assembly 23, a top assembly 24, and first and secondpreferably identical side assemblies 25 which extend between the topassembly 24 and the base assembly 23. The base, top, and side assembliesmay each comprise any of a wide array of suitable structures, includingmulti-piece structures. However, in many preferred embodiments, the baseassembly 23 comprises a base 26, such as a base plate, which supportsthe capsule filter 13 and on which the capsule filter 13 rests. Further,the side assemblies 25 each comprise side plates 30 which are connectedto the base 26. The side plates 30 preferably extend parallel to eachother closely along the exterior of the sides of the manifold 12 to thetop assembly 24. The manifold 12 may include guide channels 29 withinwhich the side plates 30 slide, e.g., upwardly and downwardly, as thecarriage 11 moves between the disengaged and engaged positions.Alternatively, the manifold may include pins or rollers which engageslots or tracks on the side plates. In addition, the top assembly 24comprises a top plate 31 which is connected to the side plates 30 andextends along the top of the manifold 12. The carriage 11 thus surroundsthe exterior of the manifold 12 and is preferably accessible formaintenance without having to disturb the manifold 12, e.g., dismantlethe manifold 12 from the pump 17.

[0092] As another example, the carriage may comprise a base assembly andopposite side assemblies without a top assembly. The carriage may thenbe operatively associated with the manifold in any suitable manner, forexample, by connecting the side assemblies of the carriage to the sidesor the bottom of the manifold via a mounting mechanism. As yet anotherexample, the carriage may be operatively associated with a structureother than the manifold. For example, when the manifold is attached to apump, the carriage may also be coupled to the pump, rather than themanifold, and arranged to move the capsule filter between engagement anddisengagement with the manifold.

[0093] In many preferred embodiments, the base plate and the side platescomprise a generally U-shaped assembly adapted to support the capsulefilter, and the carriage thus comprises a compact, highly spaceefficient structure for supporting the capsule filter. For example, thecarriage and the capsule filter may be installed in a space having arelatively small width, e.g., a width of about 60 millimeters or less,compared to a width of about 140 millimeters or more required for manyconventional filter mounting mechanisms. The capsule filter 13 can thusbe mounted and dismounted within a 60-millimeter-wide front area.Especially when combined with a 60 millimeter-wide pump, the filtrationsystem provides a dispensing system that has a high space utilizationefficiency but is nonetheless easily accessible and therefore easy touse and maintain.

[0094] In the disengaged position, the carriage preferably supports thefilter capsule on the base assembly. The filtration system may alsoinclude a positioning mechanism which allows the capsule filter to bepositioned and oriented on the base assembly with the fittings of thecapsule filter at least roughly aligned with the fittings of themanifold. The positioning mechanism may be operatively associated withthe carriage and/or the capsule filter and may take a variety of forms.In the embodiment of FIGS. 1-4, the positioning mechanism 32 iscooperatively arranged with the base 26 and may include a rear wall 33which limits the rearward movement of the capsule filter 13. The rearwall may extend from the base assembly or from one or both of the sideassemblies. Further, the positioning mechanism 32 may include an openingsuch as an elongated slot 34 which extends within the base 26 from thefront edge and a corresponding elongated tab or protrusion 35 whichextends from the bottom of the capsule filter 13. The slot 34 and theprotrusion 35 may be dimensioned to limit the rearward movement of thecapsule filter 13 on the base 26 and/or to angularly orient the capsulefilter 13 on the base 26 with the fittings 15, 14 at least roughlyaligned with one another. With the capsule filter 13 positioned on thebase 26, the capsule filter 13 may slide rearwardly along the base 26with the protrusion 35 sliding within the slot 34. The close proximityof the sides of the slot 34 and the sides of the protrusion 35 maintainthe capsule filter 13 at a desired angular orientation with respect tothe manifold 12. Once the backside of the capsule filter 13 contacts therear wall 33 and/or the backside of the protrusion 35 contacts thebackside of the slot 34, the axes of the fittings 14, 15 are at leastroughly aligned axially. The capsule filter 13 may then be mounted tothe manifold 12 without damaging the fittings 14, 15 due tomisalignment.

[0095] The positioning mechanism is not limited to the embodiment shownin FIGS. 1-4. For example, as shown in FIGS. 5 and 6, the rear wall maybe eliminated and the positioning mechanism may comprise openings suchas one or more holes 36 in the base 26 and one or more correspondingprotrusions 37 extending from the bottom of the capsule filter 13. Thecapsule filter 13 is positioned on the base 26 with the protrusions 37of the capsule filter 13 disposed in the holes 36 of the base 26. Theprotrusions 37 and the holes 36 are dimensioned and located on thecapsule filter 13 and the base 26, respectively, such that when theprotrusions 37 are disposed in the holes 36, the fittings 14, 15 of themanifold 12 and the capsule filter 13 are at least roughly alignedaxially. The embodiment shown in FIGS. 5 and 6 has two holes 36 and twoprotrusions 37. However, the positioning mechanism may comprise morethan two holes and protrusions, e.g., three holes and protrusions spacedfrom one another in a triangular configuration, or only one hole andprotrusion, e.g., an elongated hole 28 (and a corresponding protrusion)as shown in FIG. 7. Further, while the positioning mechanisms of theillustrated embodiments have been associated with the base assembly, thepositioning mechanism maybe associated with the carriage in other ways,e.g., with the side assemblies.

[0096] Once the capsule filter 13 is positioned on the carriage 11, thecarriage 11 is moved from the disengaged position toward the engagedposition by the mounting mechanism. The mounting mechanism may also takea variety of forms, and one example of a mounting mechanism 16 is shownin FIGS. 1-4. The mounting mechanism 16 is preferably cooperativelyarranged between the carriage 11 and the manifold 12 and in someembodiments may comprise a threaded arrangement including a threadedstud 40 and a mating nut 41, which may be part of a knob 42. Thethreaded stud 40 may have trapezoidal threads and is preferably fixedlymounted to the top of the manifold 12 extending toward the top assembly24 of the carriage 11. The nut 41 is correspondingly threaded and ispreferably rotatably mounted to the top assembly 24, e.g., the top plate31, to receive the stud 41 in threaded engagement. As the knob 42 isrotated in one direction, the nut 41 moves axially in one directionalong the stud 40, e.g., away from the manifold 12, and, in turn, movesthe base 26 of the carriage 11 from the disengaged position toward themanifold 12 and the engaged position, where the fittings 15 of thecapsule filter 13 engage the fittings 14 of the manifold 12. As the knob42 is turned in the opposite direction, the nut 41 moves axially in theopposite direction along the stud 40 (e.g., toward the manifold 12) and,in turn, moves the base 26 of the carriage 11 back toward the disengagedposition. The threads may be arranged to provide a quick release of thecapsule filter 13 from the manifold 12. For example, the threads may bearranged such that turning the knob 42 in the range from about 90degrees to about 360 degrees may be enough to release the capsule filter13 from the manifold 12.

[0097] Alternatively, the mounting mechanism may comprise a threadedstud and a correspondingly threaded portion of the top assembly of thecarriage, which receives the threaded stud. One end of the threaded studmay be part of a knob and the opposite end of the stud may bear against,or may be rotatably fixed to, the top of the manifold. This embodimentof the mounting mechanism operates in a manner similar to the mountingmechanism 16 shown in FIGS. 1-4.

[0098] Another example of a mounting mechanism 16 is shown in FIGS.8-13. (Components of the embodiment shown in FIGS. 8-13 have the samereference numbers as the analogous components of the embodiments shownin FIGS. 1-7.) The mounting mechanism 16 shown in FIGS. 8-13 ispreferably cooperatively arranged between the carriage 11 and themanifold 12 and may comprise a pivotable lever arrangement including alever 51 which is pivotable about a pivot axis 52. The lever may becoupled between the manifold and the carriage in a variety of ways. Forexample, the lever 51 may be pivotably mounted by pivot pins 53 to abracket 54 which, in turn, is mounted to the top of the manifold 12.Alternatively, the lever 51 may be mounted to brackets on the sides ofthe manifold. The lever 51 may also be mounted to the carriage 11 in avariety of ways, e.g., to the side assemblies 25. The lever 51 ispreferably arranged to lift the carriage 11 from the disengaged positiontoward the engaged position as the lever 51 is lifted and to lower thecarriage 11 from the engaged position toward the disengaged position asthe lever 51 is lowered. The mounting mechanism 16 may also include aspring arrangement 55 for biasing the lever 51 toward a lifted and/orlowered position, maintaining the carriage 11 in the engaged and/ordisengaged position.

[0099] Other examples of mounting mechanisms, e.g., mounting mechanismscomprising a cam arrangement, are shown in FIGS. 14-20. (Again,components of the embodiments shown in FIGS. 14-20 have the samereference numbers as the analogous components of the embodiments shownin FIGS. 1-13.) For example, the mounting mechanism 16 shown in FIGS. 14and 15 may comprise a removable or fixed lever 61 connected to arotatable shaft 62 which, in turn, is rotatably connected to themanifold 12 by a mounting plate 63. The lever 61 extends through a camslot 64 in a head 65 which may be fixedly attached to the top assembly24 of the carriage 11, e.g., at the top plate 31. As the lever 61 ismoved along the cam slot 64, the head 65 and hence the carriage 11 israised or lowered between the disengaged position and the engagedposition.

[0100] A similar mounting mechanism 16 is shown in FIGS. 16 and 17. Themounting mechanism 16 may include a pin 66 which extends radially fromthe rotatable shaft 62. The pin 66 is disposed in the cam slot 64 of thefixed head 65. The cam slot 64 may extend completely through the head65, as in the embodiment shown in FIG. 14, or it may merely extendpartially into the inner periphery of the head 65. A structure 67 formedat the end of the shaft 62 may be engaged by a wrench, e.g., an allenwrench, to turn the shaft 62. Alternatively, the shaft may extendaxially beyond the head and the protruding end of the shaft may beformed as a knob which may be turned manually. As the shaft 62 isturned, the pin 66 rides along the cam slot 64, and the head 65 andhence the carriage 11 is raised or lowered between the disengagedposition and the engaged position.

[0101] Another example of a mounting mechanism 16 which comprises a camarrangement is shown in FIGS. 18-20. The mounting mechanism 16 mayinclude a nonrotatable shaft 71 fixed to the manifold 12 and having aradially extending pin 72. The pin 72 is disposed in a cam slot 73 of ahead 74 which is rotatably attached to the top assembly 24 of thecarriage 11 by a mounting plate 75. Holes 76 in the head 75 receive aremovable lever 77, e.g., a screwdriver, which can be used to rotate thehead 74 on the shaft 71. Alternatively, the lever may be fixed to thehead; the head may be formed with a structure that can be turned with awrench; or the head may be formed as a knob that can be turned manually.As the head 75 is rotated, the pin 72 rides along the cam slot 73, andthe head 74 and hence the carriage 11 is raised or lowered between thedisengaged position and the engaged position.

[0102] As the carriage 11 is moved toward the manifold 12 from thedisengaged position to the engaged position, the fittings 15 of thecapsule filter 13 approach the fittings 14 of the manifold 12. Thefittings 14, 15 may be at least roughly aligned by the positioningmechanism. However, to more closely align the fittings 14, 15, thefiltration system 10 may include a centering mechanism which closelyaligns the axes of the fittings 14, 15 as they engage one another. Thecentering mechanism may be configured in a wide variety of ways. Forexample, the centering mechanism 80 may comprise one or, preferably, aplurality of centering protrusions, e.g., centering pins 81, which fitinto corresponding centering apertures 82 as the fittings 14, 15 engageeach other. As shown in FIG. 21, the centering pins 81 may extendupwardly from the capsule filter 13, e.g., the top of the capsule filter13, and the corresponding centering apertures 82 may be disposed in themanifold 12, e.g., the bottom of the manifold 12. Alternatively, asshown in FIGS. 22 and 23, the centering pins 81 may extend from thebottom of the manifold 12 and the centering apertures 82 may be disposedin the top of the capsule filter 13.

[0103] The centering mechanism 80 is preferably located and dimensionedto ensure that the fittings 14, 15 are closely axially aligned as theysealingly contact one another. For example, the centering pins 81 andapertures 82 may have relatively close tolerances and may be arranged toclosely engage one another before the fittings 14, 15 fully contact andare completely sealed to one another. With the centering pins 81 closelyengaged with the centering apertures 82, the fittings 14 of the manifold12 may be moved into full sealing contact with the fittings 15 of thecapsule filter 13. The centering mechanism 80 thus prevents incompletesealing and/or damage to the fittings 14, 15 due to misalignment Thecentering mechanism 80 may also serve as a stop, limiting the advance ofthe fittings 14, 15 within each other and preventing over compression.Alternatively, stops may be provided elsewhere on the manifold and thecapsule filter and/or the carriage.

[0104] As the carriage 11 is moved away from the manifold 12 from theengaged position to the disengaged position, the fittings 15 of thecapsule filter 13 may be disengaged from the fittings 14 of the manifold12. In some embodiments, the fittings 14, 15 of the manifold and thecapsule filter 13 may remain engaged as the carriage 11 is moved to thedisengaged position, the base assembly 23 of the carriage 11 moving awayfrom the bottom of the capsule filter 13 as the carriage 11 moves to thedisengaged position. The capsule filter 13 may then be removed from themanifold 12, e.g., by manually disengaging the fittings 15 of thecapsule filter from the fittings 14 of the manifold 12.

[0105] Alternatively, the filtration system 10 may further comprise adisengagement mechanism which is operatively associated with the capsulefilter 13 and automatically disengages the fittings 15 of the capsulefilter 13 from the fittings 14 of the manifold 12 as the carriage 11moves toward the disengaged position. The disengagement mechanism may beconfigured in a variety of ways. For example, the disengagementmechanism may be cooperatively arranged between the capsule filter 13and the manifold 12. One example of such a disengagement mechanism 22 isshown in FIGS. 22 and 23 and comprises one or more springs 86 disposedbetween the capsule filter 13 and the manifold 12. The springs may bepositioned in a variety of suitable locations between the capsule filterand the manifold. In the illustrated embodiment, a spring 86 is disposedaround each centering pin 81. The springs 86 are compressed around thecentering pins 81 as the carriage 11 is lifted to the engaged positionby the mounting mechanism 16 and the fittings 15 of the capsule filter13 are lifted into sealing contact with the fittings 14 of the manifold12. As the carriage 11 is lowered to the disengaged position by themounting mechanism 16, the springs 86 expand and automatically disengagethe fittings 14, 15. The centering mechanism 80 also helps to maintainaxial alignment of the fittings 14, 15 as the fittings 14, 15 aredisengaged by the disengagement mechanism 22. The capsule filter 13remains on the base assembly 23 of the carriage 11 as the carriage 11 ismoved to the disengaged position

[0106] In other embodiments, the disengagement mechanism may becooperatively arranged between the capsule filter 13 and the carriage11. One example of such a disengagement mechanism 22 is shown in FIGS. 1and 4 and comprises one or more push rods 91 disposed between thecarriage 11 and the capsule filter 13. The push rods may be positionedin a variety of suitable locations between the capsule filter and thecarriage. In the illustrated embodiment, the push rods 91 are disposedin through holes 92 in the manifold 12 between the top of the capsulefilter 13 and the top assembly 24 of the carriage 11. The push rods 91may be lifted along with the capsule filter 13 and the carriage 11 asthe carriage 11 is moved to the engaged position by the mountingmechanism 16. As the carriage 11 is lowered to the disengaged positionby the mounting mechanism 16, the top assembly 24 of the carriage 11 maybear against the push rods 91. The push rods 91, in turn, bear againstthe top of the capsule filter 13, forcing the capsule filter 13 awayfrom the manifold 12 and automatically disengaging the fittings 14,15.The capsule filter 13 remains on the base assembly 23 of the carriage 11as the carriage 11 is moved to the disengaged position.

[0107] Another example of a disengagement mechanism 22 cooperativelyarranged between the carriage 11 and the capsule filter 13 is shown inFIGS. 24 and 25. (Components of the embodiment shown in FIGS. 24 and 25have the same reference numbers as the analogous components of theembodiment shown in FIGS. 1-4.) The disengagement mechanism 22 generallycomprises a fitment which physically couples the capsule filter 13 andthe carriage 11 as the carriage 11 moves between the engaged positionand the disengaged position The fitment may be structured in a widevariety of ways. In the illustrated embodiment the fitment 96 comprisesthe engagement of the base assembly 23 of the carriage 11 with thecapsule filter 13, e.g., with a flange 97 extending from the protrusion35 in the bottom of the capsule filter 13 past the edges of the slot 34in the base 26. As the carriage 11 is lowered to the disengaged positionby the mounting mechanism 16, the base 26 of the carriage 11 bearsagainst the flange 97 of the capsule filter 13, forcing the capsulefilter 13 away from the manifold 12 and automatically disengaging thefitting 15 of the capsule filter 13 from the fittings 14 of the manifold12. The capsule filter 13 remains on the base assembly 23 of thecarriage as the carriage 11 is moved to the disengaged position.

[0108] Another example of a fitment is a flange which extends from eachside assembly of the carriage over the top of the capsule filter. As thecarriage is lowered by the mounting mechanism, the flanges of the sideassemblies may bear against the top of the capsule filter, automaticallydisengaging the capsule filter from the manifold.

[0109] The manifold 12 may also be configured in a wide variety of ways.For example, the manifold may have any regular or irregular shape. Asshown in FIGS. 1-4, the manifold 12 may have a box-shaped configurationincluding a front 100, a back 101, a top 102, a bottom 103 and oppositesides 104, 105. The manifold 12 may further include one or more conduitsfor transporting fluid to and/or from the capsule filter. Each of theconduits is preferably configured to reduce hold up volume and to avoiddead volumes or zones where the fluid can stagnate.

[0110] In many preferred embodiments, the manifold 12 is fluidly coupledto a pump 17. For example, the manifold 12 may be directly attached tothe pump 17, e.g., along the back 101 of the manifold 12. The outlet ofthe pump 17 may be connected to an inlet conduit of the manifold 12which extends through the manifold 12 and fluidly communicates, in turn,with the inlet fittings 14 a, 15 a of the manifold 12 and the capsulefilter 13. Alternatively, the inlet conduit may be at least partiallyexternal to the manifold, e.g., extending externally from the pump tothe manifold and hence to the inlet fittings. The manifold 12 may alsoinclude an outlet conduit 21 which fluidly communicates between theoutlet fittings 14 b, 15 b and any other appropriate component of thefluid system downstream of the manifold 12. In the illustratedembodiment, the outlet conduit 21 may extend from the outlet fittings 14b, 15 b through the manifold 12 to the front 100 of the manifold 12.However, the outlet conduit may extend from any portion of the manifold,including the top of the manifold. The manifold 12 may further include avent conduit 20 which fluidly communicates between the vent fittings 14c, 15 c and any appropriate reservoir for the vented gas. Again in theillustrated embodiment, the vent conduit 20 may extend from the ventfitting 14 c, 15 c through the manifold 12 to the front 100 of themanifold 12. However, the vent conduit may extend from any portion ofthe manifold, including the top of the manifold. In some embodiments,the vent conduit, as well as the vent fittings, may be eliminatedentirely.

[0111] The number and configuration of the fittings 14 of the manifold12, as well as the fittings 15 of the capsule filter 13, may be widelyvaried. In many embodiments the manifold 12 has three fittings 14 a, 14b, 14 c. However, a manifold may have more than three fittings or fewerthan three fittings. For example, where a vent is not preferred or wherethe inlet to the capsule filter or the outlet from the capsule filter isnot directed through the manifold, the manifold may have two fittings oronly a single fitting.

[0112] The fittings 14 of the manifold 12, as well as the fittings 15 ofthe filter cartridge 13, may be structured in a variety of ways. Forexample, the fittings may be arranged in any regular of irregularpattern, such as a triangular pattern. Preferably, the fittings 14, 15are generally aligned. Further, the spacing between the fittings, or thepattern of the fittings, may be symmetric but is preferably notsymmetric. For example, as shown in FIG. 2, the distance between thevent fittings 14 c, 15 c and the outlet fittings 14 b, 15 b may be lessthan the distance between the outlet fittings 14 b, 15 b and the inletfittings 14 a, 15 a A unsymmetric spacing or pattern helps to preventthe capsule filter from being installed “backwards” on the manifold.

[0113] The fittings may be structured in various ways. For example, eachof the fittings may comprise a nozzle or a port or receptacle whichreceives a nozzle. Some of the fittings on the manifold, or the capsulefilter, may comprise nozzles while others comprise receptacles, or allof the fittings on the manifold may comprise nozzles or receptacles. Inthe illustrated embodiment, the fittings 14 a, 14 b, 14 c of themanifold 12 all preferably comprise nozzles 110 and the fittings 15 a,15 b, 15 c of the capsule filter 13 all preferably comprisecorresponding receptacles 111 which receive the nozzles 110 of themanifold 12.

[0114] A wide assortment of nozzles and receptacles are suitable.However, the nozzle preferably includes a tip portion which contacts,and more preferably seals against, a corresponding surface in thereceptacle. By contacting and/or sealing the tip portion of each nozzlewith a corresponding surface in the receptacle, gaps or leakage volumesat the ends of the nozzles are eliminated, reducing the hold up volumeand minimizing stagnant flow areas or dead zones within the filtrationsystem, and the filtration system may be made smaller. To enhance thesealing engagement of the contact surface of the tip portion of eachnozzle and the corresponding contact surface of the receptacle, at leastthe contact surface of the tip portion of the nozzle and the contactsurface of the receptacle are preferably formed from differentmaterials, one harder and the other of similar hardness or, morepreferably, somewhat softer or more deformable. As the tip portion ofthe nozzle engages the contact surface of the receptacle, the softermaterial deforms to the harder material, forming a highly effectiveseal. The sealing engagement of the contact surface of the tip portionof the nozzle and the contact surface of the receptacle is preferablyfree of any additional sealing member, such as a gasket, at thecontacting surfaces and may comprise the only or the primary sealbetween the fittings. However, additional seals spaced from thecontacting surfaces, such as a supplemental O-ring seal, may also beprovided between the nozzle and the receptacle. The seal formed by thecontact surfaces may, for example, prevent any dead zones or stagnantportions from developing at the ends of the nozzle, while thesupplemental O-ring seal may ensure a liquid and/or air tight sealbetween the fittings.

[0115] Either the tip portion of the nozzle or the contact surface ofthe receptacle may be formed from the harder material or the softermaterial. Because the capsule filter is preferably disposable and themanifold is preferably reusable, it is preferable to form the fitting onthe manifold, e.g., either the nozzle or the receptacle on the manifold,from the harder material. Examples of harder materials include metal,such as stainless steel, and polymeric materials, such as polyethylene,e.g., HDPE, polypropylene, PFA, ETFE, ECTFE, and PCTFE(polychlorotrifluoroethylene), which may be relatively harder than thematerial in the corresponding fitting. Examples of softer materialsinclude elasomeric-type materials, such as rubber, silicone, andpolyurethane, and polymeric materials, such as LDPE, FEP, PFA and PTFE,which may be relatively softer than the material of the correspondingfitting. Generally, any suitable combination of relatively hard andrelative soft materials may be used for the nozzle/receptaclearrangements based, for example, on a shore hardness D-scale, where PTFEis in the range from about 50 to about 56; ELTFE is about 75; FEP isabout 55; PFA is about 60; PCTFE is about 90; ECTFE is about 75; PVDF isin the range from about 70 to about 80; LDPE is in the range from about40 to about 50; and HDPE and UHMWPE are in the range from about 60 toabout 70.

[0116] The nozzles and receptacles may be structured in numerous ways.(Components of the embodiments shown in FIGS. 26-41 have the samereference numbers as the analogous components of the embodiments shownin FIGS. 1-25.) Some of the many examples of nozzle/receptaclearrangements are illustrated in FIGS. 26-41. In each of the illustratedembodiments, the nozzle is operatively associated with the manifold andthe corresponding receptacle is operatively associated with the capsulefilter. However, one or more of the nozzles may alternatively beassociated with the capsule filter while the corresponding receptacle isassociated with the manifold.

[0117] In the embodiment shown in FIGS. 26 and 27, the manifold 12 maycomprise a body 115, e.g., a polymeric body, and may further comprise abottom plate 116, e.g., a metal plate, mounted to the body 115. A nozzle110, which is preferably unitarily formed with the body 115, extendsthrough an aperture 118 in the bottom plate 116. A conduit 119, e.g., aninlet, outlet, or vent conduit, extends through the body 115 and thenozzle 110, opening in the tip portion 120 of the nozzle 110.

[0118] The receptacle 111 of the capsule filter 13 may comprise a collar126, e.g., a polymeric collar, which has a region defining a bore 127. Aseat 128, which preferably comprises a separate insert, may bepositioned within the bore 127 on a ledge 129 of the collar 126. Theseat 128 may be formed from a material different from the material ofthe nozzle 110 and also different from the material of the collar 126,the seat 128 being preferably formed from a material which is softer orharder than the material of the nozzle 110 or the collar 126. Forexample, the seat 128 may be formed from PTFE while the nozzle 110 andthe collar 126 may be formed from polyethylene, PFA or PCTFE. A seal,such as an O-ring 130, may be positioned in the bore 127 on a rim of theseat 128 and around the interior of the collar 126. A cap 131 may bemounted to the collar 126 over the O-ring 130. The cap 131 has anopening 132 which is large enough to receive the nozzle 110. The opening132 in the cap 131, as well as the collar 126, the seat 128, and/or thetip portion 120 of the nozzle 110, and may be tapered to facilitateinsertion of the nozzle 110 into the receptacle 111. A conduit 133extends through the collar 126 and at least partially through the seat128 and opens onto the opening 132 in the cap 131.

[0119] The tip portion 120 of the nozzle 110 and the seat 128 each havea contact surface 140, 142 which may be similarly or differently shaped.The configuration of each contact surface 140, 142 may vary. Forexample, the contact surfaces 140, 142 of the tip portion 120 and theseat 128 may have curved or tapered configurations such as a sphericalor conical configuration or a flat annular configuration. The area ofthe contact surfaces 140, 142 may be relatively wide but in manypreferred embodiments, the area of at least one of the correspondingcontact surfaces 140, 142 may be relatively narrow.

[0120] As the carriage moves from the disengaged position to the engagedposition and the nozzle 110 is inserted into the receptacle 111, theO-ring 130 seals against the nozzle 110. The O-ring 130 may also sealagain the rim of the seat 128, the inner wall of the collar 126 and/orthe cap 131. In addition, the contact surfaces 140, 142 of the nozzle110 and the receptacle 111 engage and at least the softer surface, e.g.,the contact surface 142 of the seat 128, preferably deform toeffectively seal against the harder surface, e.g., the contact surface140 of the tip portion 120 of the nozzle 110. As the nozzle 110 bearsagainst the seat 128, not only does the contact surface 142 of the seat128 seal against the contact surface 140 of the nozzle 110, but the seat128 also deforms and seals against the collar 128, e.g., against theledge 129 and/or the inner wall of the bore 127 of the collar 126. Bycontacting and sealing the seat 128 against the tip portion 120 of thenozzle 110 and the collar 126 of the receptacle 111, no gaps or leakagevolumes are created which can hold up fluid and cause dead zones orstagnant flow areas. Instead, the channel defined by the conduits 119,133 extending through the nozzle 110 and the receptacle 111 provides aflow path free of hold up volumes, leakage volumes, and dead zones, asshown in FIG. 27.

[0121] In addition to reducing hold up volumes, leakage volumes and deadzones, the nozzle/receptacle arrangement provides a more reliablefiltration system 10 and facilitates manufacture of the manifold 12 andthe capsule filter 13. For example, the dimensional variationsassociated with the axial length of the nozzles 110, e.g., from thebottom plate 116 to the tip portion 120, may mean that nozzles 110 onthe same manifold 12 have different lengths. This variation may beaccommodated by the deformation of the seat 128. Longer nozzles 110 maydeform the seat 128 slightly more than shorter nozzles 110 while bothadequately seal the fittings.

[0122] In addition, eccentricities in the alignment and/or spacing ofthe nozzles 110 on the same manifold 12 may be accommodated by thedeformation of the seat 128 and the use of an insert for the seat 128,or the nozzle 110. The seat 128 and/or the nozzle 110 may be arranged tomove laterally as the fittings 14, 15, including the contact surfaces140, 142, contact one another. For example, the outer diameter of theseat 128 may be slightly smaller than the diameter of the bore 127 inthe collar 126, e.g., by about 0.2 mm. As the fittings 14, 15, includingthe mating tapered contact surfaces 140, 142, engage one another, theylaterally adjust the position of the seat 128 within the bore 127,centering the seat 128 on the nozzle 110. Further, any slight tilt ofthe axis of the nozzle 110 may be accommodated by an asymmetricaldeformation of the seat 128 about the axis of the nozzle 110.

[0123] Similar variations and eccentricities in the receptacle may alsobe accommodated. By accommodating these variations and eccentricities,abnormal stresses and strains on the nozzles and receptacles may berelieved, providing a more reliable filtration system. Further, neitherthe manifold nor the capsule filter need be manufactured to extremelytight tolerances, reducing the cost of manufacture.

[0124] Other examples of the nozzle/receptacle arrangements are shown inFIGS. 28-41 and may provide similar and/or additional features andadvantages. (Components of the embodiments shown in FIGS. 28-41 have thesame reference numbers as the analogous components of the embodimentshown in FIGS. 26 and 27.) The embodiment shown in FIGS. 28 and 29 isvery similar to the embodiment shown in FIGS. 26 and 27. However, ridges145 may extend from the ledge 129 of the collar 126 toward the seat 128.The engagement of the contacting surfaces 140, 142 of the nozzle 110 andthe receptacle 111 deforms the ridges 145 and/or drives the ridges 145into the seat 128 to better seal the seat 128 to the collar 126.Alternatively, the ridges may extend from the seat toward the ledge ofthe collar and may deform and/or be driven into and seal against theledge as the nozzle engages the receptacle.

[0125] In the embodiment shown in FIGS. 30 and 31, the seat 128 maycomprise a unitary portion of the collar 126 rather than an insert.However, the nozzle 110 preferably comprises an insert sealed to thebody 115 of the manifold 12, e.g., by an O-ring 146 disposed in a bore147 at the upper end of the nozzle insert. The nozzle 110 may be formedfrom a different material, e.g., a harder material, than the collar 126of the receptacle 111 and/or from a different material than the body 115of the manifold 12. Variations and eccentricities may be accommodated bymovement of the insert and by deformation of one or both contactingsurfaces, in a manner similar to that previously described. In addition,variation in the length of the nozzles 110 may be accommodated by axialcompression of the O-ring 146. The contact surfaces 140, 142 arepreferably semi-spherical and may have a relatively broad contact area.

[0126] The embodiment shown in FIGS. 32 and 33 is similar to theembodiment shown in FIGS. 30 and 31. However, both the nozzle 110 andthe seat 128 may comprise inserts. The O-ring 146 sealing the nozzleinsert is disposed in a groove 147 around the outer periphery of theinsert. Further, ridges 149 may be disposed between the nozzle insertand the body 115 of the manifold 12, in addition to the ridges 145between the seat insert and the ledge 129 of the collar 126. The ridges149 may extend from the body 115 toward the nozzle insert 110 or fromthe nozzle insert 110 toward the body 115. The engagement of thecontacting surfaces 140, 142 deforms the ridges 145, 149 and/or drivesthe ridges 145, 149 into the inserts to better seal the seat and nozzleinserts.

[0127] The embodiment shown in FIGS. 34 and 35 is similar to theembodiment shown in FIGS. 30 and 31. However, the receptacle 111 may notinclude a cap. Rather, the collar 126 may have a rim 150 which faces themanifold 12 and defines the opening 132 in the receptacle 111. TheO-ring 130 which seals against the nozzle 110 is disposed in a groove151 in the inner wall of the collar 126 which defines the bore 127. Inaddition, the contact surfaces 140, 142 preferably have a conicalconfiguration and at least one of the contact surfaces 140, 142, e.g.,the contact surface 142 of the seat 128, may have a relatively narrowcontact area, which may enhance the seal between the contact surfaces140, 142.

[0128] The embodiment shown in FIGS. 36 and 37 is similar to both theembodiment shown in FIGS. 34 and 35 and the embodiment shown in FIGS. 32and 33. The contact surface 142 of the seat insert has the relativelynarrow contact area.

[0129] The embodiment shown in FIG. 38 may comprise a nozzle 110, e.g.,a nozzle insert, which has a groove 155 in the outer wall. An O-ring 156is disposed in the groove 155 and provides a seal against the receptaclecollar 126 which supplements the sealing engagement of the contactsurfaces 140, 142.

[0130] The embodiment shown in FIG. 39 is similar to the embodimentshown in FIG. 38. However, the receptacle 111 may include a cap 131 anda seat insert 128 comprising a spherical contact surface having arelatively narrow contact area.

[0131] The embodiment shown in FIG. 40 is similar to the embodimentshown in FIG. 39. However, the tip portion 120 of the nozzle 110 mayhave a cylindrical configuration and both contact surfaces 140, 142 mayhave flat, annular configurations with relatively small contact areas.

[0132] The embodiment shown in FIG. 41 is similar to the embodimentshown in FIG. 40. However, the contact surfaces 140, 142 may have areverse conical configuration in which the cone converges toward theaxis of the nozzle 110 within the nozzle 110.

[0133] The fittings shown in FIGS. 26-41 include a nozzle and acorresponding receptacle having mating contact surfaces which preferablyserve as a seal, e.g., a primary seal or even the sole seal, between thefittings. However, other fittings between the manifold and the capsulefilter may be used. For example, fittings which are threaded, clampedand/or friction fitted to one another may be used to seal the manifoldto the capsule filter.

[0134] Filters embodying the invention be configured in a variety ofways. One example of a filter embodying the invention is a capsulefilter such as the capsule filter 13 shown in FIGS. 42-46. The capsulefilter 13 generally comprises a housing 160 and a filter cartridge 161removably or, preferably, permanently disposed in the housing 160.

[0135] The housing 160 may comprise a single piece structure but may beformed from any suitably impervious material, e.g., a metal or apolymeric material, and may have any desired shape, e.g., a generallycylindrical shape. In many preferred embodiments, the shape of thehousing corresponds to the shape of the filter cartridge.

[0136] The housing 160 preferably comprises a multi-piece structure. Forexample, the housing 160 may include a bowl 162 and a head 163 removablyor, preferably, permanently attached to the bowl 162. The bowl 162 mayinclude a side wall and a bottom wall. A handle 159 may extend outwardlyfrom the side wall of the bowl 162 and may be used to position thecapsule filter 13 on the base assembly of the carriage with theprotrusion 35 on the bottom of the capsule filter 13 engaged in the slotin the base.

[0137] The housing 160 has one or more fittings, e.g., an inlet fitting15 a, an outlet fitting 15 b, and a vent fitting 15 c. The inlet fitting15 a and the outlet fitting 15 b define a fluid flow path through thehousing 160. The fittings may be variously configured, e.g., as nozzles.In the embodiment illustrated in FIGS. 42-45, the fittings each comprisereceptacles which may be similar to any of the receptacles previouslydescribed. One or more of the fittings may be disposed in the bowl e.g.,at the bottom or in the side wall of the bowl. Preferably, however, atleast one and, more preferably, all of the fittings 15 a, 15 b, 15 c aredisposed in the head 163 on the top of the capsule filter 13.

[0138] The housing 160 preferably contains the filter cartridge 161within a filter cartridge chamber in the fluid flow path. The filtercartridge preferably includes a filter element 170 having a filtermedium, as shown in FIG. 46. The filter medium may comprise a solid orhollow porous mass, such as a cylindrical mass of sintered metalparticles or a cylindrical mass of bonded and/or intertwined fibers,e.g., polymeric fibers. In many preferred embodiments, the filter mediummay comprise a permeable sheet, e.g., a porous woven or non-woven sheetof fibers, including filaments, or a permeable or porous, supported orunsupported polymeric membrane, and the filter element 170 may have acylindrical, hollow pleated configuration. The filter medium may be thesole layer of the pleated filter element 170 but is preferably one oftwo or more layers of a pleated composite further including, forexample, one or more drainage layers, pre-filter layers, additionalfilter layers, substrates, and/or cushioning layers. The pleats of thefilter element may extend radially or, preferably, non-radially, asdisclosed, for example, in U.S. Pat. No. 5,543,047 which is incorporatedby reference. As disclosed in U.S. Pat. No. 5,543,047 non-radiallyextending pleats each have a height greater than (D−d)/2 and less thanor equal to (D²−d²)/[4(d+2t)] where D and d are the outside and insidediameters, respectively, of the pleated filter element at the crests androots of the pleat and t is the thickness of a pleat leg. Preferably,the height of each pleat is in the range from about 70% or 80% to about100% of (D²−d²)/[4(d+2t)]. The non-radial pleats may be preferredbecause there is little or no space between the pleats, minimizing holdup volume and dead zones.

[0139] The hollow filter element 170 is preferably disposed between acage 171 and a core 172. The ends of the filter element 170, the cage171 and the core 172 may be sealed to end caps 173, 174, e.g., a blindend cap 173 and an open end cap 174. The open end cap 174 has an opening175 which fluidly communicates with the interior of the hollow filterelement 170. The open end cap may be sealed or attached to the housingwith the opening in the open end cap, in turn, fluidly communicatingwith a fitting. For example, in the embodiment shown in FIGS. 42-45, theopen end cap 174 may be bonded to the head 163 with the outlet fitting15 b preferably fluidly communicating with the interior of the filterelement 170 via the opening 175 in the open end cap 174. The inletfitting 15 a preferably fluidly communicates with the exterior of thefilter cartridge 161. Flow may then be directed outside in through thefilter cartridge 161. Alternatively, the inlet fitting and the outletfitting may be arranged to fluidly communicate with the interior and theexterior, respectively, of the filter cartridge, and flow may bedirected inside out through the filter cartridge.

[0140] While the filter cartridge has been described in terms of ahollow filter element 170 having a pleated filter medium, a cage 171, acore 172 and end caps 173, 174, the filter cartridge is not limited tothis embodiment. Numerous alternative filter cartridges are suitable.For example, the filter element may have a filter composite which isspirally wound rather than pleated. The cage and/or the core may beeliminated. Further, one or both end caps may be eliminated, and theends of the filter element may be bonded directly to the top and/orbottom of the housing.

[0141] Yet other examples of filter cartridges may incorporate filtermedia comprising permeable hollow fiber media. For example, as shown inFIG. 47, a capsule filter 13 may comprise a filter cartridge 161 whichmay include permeable, e.g., porous, hollow fibers 180. (Components ofthe embodiment shown in FIG. 47 have the same reference numbers as theanalogous components of the embodiment shown in FIG. 45.) The hollowfibers 180 may be contained between end caps 181, 182, e.g., an open endcap 181 and a blind end cap 182. In particular, the hollow fibers 180may be potted in and extend from a partition 183 of the open end cap 181and loop back to the partition 183, one or both of the ends of thehollow fibers 180 being an open end fluidly communicating with theopening 184 in the open end cap 181. A perforated cage 185 may extendbetween the end caps 181, 182 around the hollow fibers 180.Alternatively, both end caps may be open end caps and the cage may haveno openings, the fluid being directed into the filter cartridge throughthe open lower end cap, or the cage and the blind end cap may beeliminated.

[0142] Another example of a capsule filter 13 comprising permeablehollow fibers 180 is shown in FIG. 48. (Components of the embodimentshown in FIG. 48 have the same reference numbers as the analogouscomponents of the embodiment shown in FIG. 47.) In the embodiment shownin FIG. 48, the hollow fibers 180 extend between the partition 183 inthe open end cap 181 and the blind end cap 182. One end of each hollowfiber 180 may be blindly potted in the blind end cap 182, while theother end is openly potted in the partition 183 in fluid communicationwith the opening 184 in the open end cap 181. A perforated cage may ormay not extend between the end caps.

[0143] Regardless of the configuration of the filter cartridge, theinterior of the housing is preferably fitted to the filter cartridge tominimize hold up volume and dead zones and to enhance fluid flowdistribution and rise time within the housing. For example, as shown inFIG. 45, the interior side wall of the bowl 160 and the exterior of thefilter cartridge 161 may be similarly shaped, and the bowl 160preferably fits closely completely around the filter cartridge 161,defining an annular fluid flow distribution channel between the interiorof the bowl 160 and the exterior of the filter cartridge 161. Theannular channel is preferably dimensioned to reduce hold up volume andto allow a sweep of fluid flow around and/or axially along the filtercartridge without undue pressure drop between the inlet and outletfittings. The desired dimensions of the annular channel may bedetermined empirically based on such factors as, for example, theviscosity of the fluid, the desired flow rates and pressure drop limitsand the area of the inlet or outlet, e.g., the inlet fitting or theoutlet fitting. For many embodiments, the axial cross sectional area ofthe annular channel may preferably be on the order of, e.g.,approximately equal to, the area of the inlet nozzle.

[0144] Further, the interior bottom wall of the bowl 160 and the bottomof the filter cartridge 161 may also be similarly shaped and closelyfitted to one another. The bottom of the filter cartridge may completelycontact and may be attached to the bottom wall of the bowl, eliminatingany space between them. However, in many preferred embodiments, thebottom of the filter cartridge is fitted to the bottom of the housingwith one or more lower flow channels extending between them andcommunicating with the bottom of the annular flow channel. For example,the bottom of the filter cartridge, e.g., the bottom of the lower endcap, and/or the interior bottom wall of the housing may have one or moreradially extending ribs or spokes. The filter cartridge and the housingmay contact one another along the ribs and define the lower channelsbetween them. Further, the interior bottom wall of the housing and/orthe bottom of the filter cartridge preferably have a surface which isinclined upwardly to decrease the rise time of bubbles from the bottomof the filter. For example, the lower flow channels may incline upwardlytoward the annular channel preferably at an angle of bout 15° or less,e.g., about 10°. or less. The lower channels are preferably dimensionedto reduce hold up volume, to allow a sweep of fluid flow between thefilter cartridge and the bottom of the housing without undue pressuredrop between the inlet and outlet fittings, and/or to facilitateclearance of bubbles from the bottom of the filter. Again, the desireddimensions, including the degree of incline, of the lower channels maybe determined empirically based factors such as fluid viscosity, desiredflow rates, pressure drop limits and inlet/outlet areas.

[0145] The interior wall of the head 163 may fit closely to the top ofthe filter cartridge away from the vent fitting 15 c but is preferablyat least slightly spaced from the top of the filter cartridge 161 in thevicinity of the vent fitting 15 c, allowing gases to rise from theannular flow distribution chamber and over the top of the filtercartridge 161 toward the vent fitting 15 c. Preferably, the spacebetween the interior wall of the head 163 and the top of the filtercartridge 161, e.g., the top of the upper end cap, increasescontinuously from a location most distant from the vent fitting 15 c tothe vent fitting 15 c. Nonetheless, while the space between the interiorwall of the head 163 and the top of the filter cartridge 161 ispreferably sufficient to vent gas from the capsule filter 13, it is alsopreferably small enough to avoid excessive hold up volume.

[0146] In many, but not all, preferred embodiments, the housing maycomprise a fluid conduit, e.g., a fluid inlet conduit or a fluid outletconduit, which extends from one of the fittings axially along theperiphery of the filter cartridge chamber and is isolated from thefilter cartridge chamber along a substantial length of the conduit,e.g., at least about 50 percent of the length of the conduit. Forexample, the fluid conduit may be disposed in the bowl, or adjacent tothe bowl, and radially beyond the filter cartridge chamber. Preferably,the fluid conduit extends from a fitting at the top of the housing andopens into the filter cartridge chamber, e.g., the annular flowdistribution channel, at the bottom of the housing. As shown in FIG. 45,the fluid conduit 164 may comprise an inlet conduit extending axiallyalong the periphery of the filter cartridge chamber from the inletfitting 15 a at the top of the housing 160 through the head 163 and thebowl 162 to the bottom of the housing 160. The inlet conduit 164preferably communicates with the annular fluid flow distribution channeland the filter cartridge chamber only at the bottom of the housing 160and, therefore, is isolated from the filter cartridge chamber for atleast about 70 percent, more preferably at least about 80 percent or atleast about 90 percent, of the length of the conduit 164.

[0147] The housing may also preferably comprise a radial passage throughthe side wall and/or more preferably in the interior bottom wall of thehousing which extends from the side wall of the bowl 162 and fluidlycommunicates with the axial fluid conduit. The radial passage may extendalong the lower end cap or along the bottom wall of the housing or alongboth, e.g., between the lower end cap and the bottom wall. For example,the radial passage may extend from the bottom of the fluid conduit,under the filter cartridge, e.g., under the lower end cap. The radialpassage may extend completely under the filter cartridge but preferablyextends only part way under the filter cartridge. As shown in FIG. 45,the radial passage 165 extends from the bottom of the fluid conduit 164under the filter cartridge 161, terminating near the center of thefilter cartridge chamber of the housing 160. The radial passage 165 mayhave a uniform cross section or a tapered cross section, e.g., the crosssection may decrease with increasing distance from the side wall of thebowl 162. The radial passage 165 may feed fluid to, or receive fluidfrom, the lower flow channels between the bottom of the filter cartridge161 and the bottom wall of the bowl 162 and may fluidly communicatebetween the lower flow channels and the axial fluid conduit.Alternatively, the radial passage may be eliminated, e.g., where thereare no lower flow channels between the bottom of the filter cartridgeand the bottom wall of the bowl.

[0148] Further, in many preferred embodiments the filter cartridge maycomprise a keying mechanism cooperatively arranged between the housingand the filter cartridge to center the filter cartridge in the filtercartridge chamber of the housing and provide a uniform annular flowchannel. The keying mechanism may have any of numerous suitablestructures. For example, the keying mechanism may comprise one or morecentering pins and mating centering apertures on the housing and thefilter cartridge similar to the centering mechanism 80 previouslydescribed.

[0149] More preferably, one or both of the end caps, e.g., the lower endcap and the corresponding wall of the housing may have mating shapeswhich center the filter cartridge in the filter cartridge chamber as thefilter cartridge is mounted within the housing. The shapes may, forexample, comprise curved or tapered configurations, e.g., a partiallyspherical, elliptical or conical configuration, on one or both end capsand the corresponding wall of the housing. As shown in FIG. 45, thelower end cap 173 may have a generally conical configuration which mateswith a conical configuration in the interior bottom wall of the bowl 162of the housing 160. The configurations are located and shaped to centerthe filter cartridge 161 in the filter cartridge chamber. Thus, as thefilter cartridge 161 is mounted within the bowl 162 with theconfiguration of the lower end cap 173 contacting the configuration ofthe interior bottom wall of the bowl 162, the filter cartridge 161automatically centers itself within the filter cartridge chamber of thebowl 162 due to the mating engagement of the conical configurations. Thehead 163 may then be attached to the bowl 162 and the upper end cap 174of the filter cartridge 161. A keying mechanism, such as matingconfiguration, e.g., conical configuration, in the interior wall of thehead 163, e.g., the region of the head 163 near the outlet fitting 15 b,and on the upper end cap 174, may center the filter cartridge 161 on thehead 163 as well as the bowl 162.

[0150] The housing including one or more of the axial fluid conduit, theradial passage, and/or the keying mechanism may be fabricated in anysuitable manner. For example, a molded bowl 162 is illustrated FIGS. 49and 50. The bowl 162 may be molded in two pieces, e.g., a side wallpiece 195 and a bottom wall piece 196, and the two pieces 195, 196 maybe attached, e.g., welded or bonded, to form the bowl 162. In theillustrated embodiment, the bowl 162 includes an axial fluid conduit164,a radial passage 165, a filter cartridge chamber, and a centeringconfiguration 191 in the interior bottom wall of the bowl 162.

[0151] Alternatively or additionally, the housing may be machined. Forexample, a machined bowl 162 is illustrated in FIGS. 51 and 52. Themachined bowl 162 preferably comprises a unitary piece 197. A filtercartridge chamber and an axial fluid conduit 164 may be bored in theunitary piece 197. A radial passage 165 may be bored through the sidewall of the unitary piece 197, and the exterior end of the radialpassage 165 may be plugged or fitted with a fitting.

[0152] Other examples of capsule filters which embody the invention andwhich may be used in one or more of the previously disclosed filtrationsystems are shown in FIGS. 53-58, all of which may provide similarand/or additional features and advantages of the embodiment shown inFIG. 45. (Components of the embodiments shown in FIGS. 53-58 have thesame reference numbers as the analogous components of the embodimentshown in FIG. 45.) The embodiment of the filter shown in FIG. 53 may besimilar to the embodiment shown in FIG. 45. The capsule filter 13 shownin FIG. 53 may include an axial fluid conduit 168, a radial passage 165,and a keying mechanism such as mating configurations on the lower endcap 173 and the interior bottom wall of the bowl 162 and/or on the upperend cap 174 and the interior wall of the head 163. Further, the housing160 may closely fit to the filter cartridge 161, and/or the filtercartridge 161 may have non-radially extending pleats. However, thefittings 15 a, 15 b, 15 c of the capsule filter 13 shown in FIG. 53 maydiffer from the fittings 15 a, 15 b, 15 c of the capsule filter 13 shownin FIG. 45. Examples of various other types of fittings 15 which may beused with this or any of the other embodiments of the filter are shownin FIG. 54.

[0153] The embodiment of the filter shown in FIG. 55 is similar to theembodiment shown in FIG. 53. The capsule filter 13 shown in FIG. 55, aswell as the capsule filter 13 shown in FIG. 56, may also include anaxial fluid conduit 164, a radial passage 165, a keying mechanism, e.g.,an upper keying mechanism and/or a lower keying mechanism, a close fitbetween the housing 160 and the filter cartridge 161, and/or a filtercartridge having non-radially extending pleats. However, in the capsulefilter 13 shown in FIG. 55 the bowl 162 and the filter cartridge 161 maybe longer than those in the embodiment of FIG. 53.

[0154] The embodiment shown in FIG. 56 is similar to the embodimentshown in FIG. 55. However, the capsule filter 13 shown in FIG. 56 mayhave a head 163 which is removably mounted to the bowl 162. The head maybe removably fastened to the bowl in any suitable manner. For example,the head 163 may be fastened to the bowl 162 by a ring nut 200. One ormore O-rings 201 may be used to seal the head 163 to the bowl 162.Alternatively, the heat may be threaded directly to the bowl or boltedto the bowl.

[0155] The embodiment of the filter shown in FIGS. 57 and 58 may beuseful in one or more of the previously disclosed filtration systems,including the filtration system 10 shown in FIGS. 8-13. The capsulefilter 13 may include an axial fluid conduit 164, a radial passage 165,and a keying mechanism. The keying mechanism may comprise dissimilarshapes on the lower end cap 173, e.g., a generally conical shape, and onthe interior bottom wall of the bowl 162, e.g., a generally cylindricaldepression, which nonetheless fit to each other to center the filtercartridge 161 in the filter cartridge chamber. The open exterior end ofthe radial passage 165 in the housing 160 may be plugged or may beequipped with a fitting, as previously disclosed.

[0156] Filters embodying the present invention may be useful in any ofthe previously disclosed filtration systems, but the invention is notlimited to these embodiments. For example, capsule filters which embodythe invention or may but may not be useful in the previously disclosedfiltration systems are shown FIGS. 59-63. (Components of the embodimentsshown in FIGS. 59-63 have the same reference numerals as the analogouscomponents of the embodiments shown in FIG. 45 and the FIGS. 53-58.) Theembodiment shown in FIGS. 59 and 60 may have an N-type fittingarrangement. The inlet fitting 15 a may be disposed, for example, in thebottom wall of the bowl 162. Fluid enters the capsule filter 13 via aconduit which extends from the inlet fitting 15 a to lower fluidchannels between the lower end cap 173 and the interior bottom wall ofthe bowl 162. From the lower fluid channels, the fluid flows to theannular fluid distribution channel between the filter cartridge 161 andthe housing 160. The fluid may thus sweep evenly under the filtercartridge 161 radially and along the length of the filter cartridge 161axially. The outlet fitting 15 b and the vent fitting 15 c may bedisposed in the head 163. A keying mechanism, such as matingconfigurations, may be arranged between the lower end cap 173 and theinterior bottom wall of the bowl 162 and/or between the upper end cap174 and the interior wall of the head 163. The housing 160 may fitclosely around the filter cartridge 161 and/or the filter cartridge 161may include non-radially extending pleats.

[0157] The embodiment of the filter shown in FIGS. 61 and 62 may besimilar to the embodiment shown in FIGS. 59 and 60. For example, thecapsule filter 13 shown in FIGS. 61 and 62 may have a keying mechanismat the top and/or the bottom of the capsule filter 13, a housing 160which fits closely to the filter cartridge 161, and/or a filtercartridge 161 which has non-radially extending pleats. However, capsulefilter 13 may have an L-type fitting arrangement wherein the inletfitting 15 a may be disposed in the housing 160 at the side of thehousing 160. A radial passage 165 extends from the inlet fitting 15 aand fluidly communicates with the lower channels in the housing 160 andhence the angular flow distribution channel around the filter cartridge161. In some of the previous embodiments, the top portion of the radialpassage was open to the annular channel and the lower channels alongmuch of the length of the radial passage. In the capsule filter 13 shownin FIGS. 61 and 62, the radial passage 189 may be isolated from thefilter cartridge chamber over much of its length, e.g., between theinlet fitting 15 a and the lower channels at the center of the filtercartridge 161.

[0158] The embodiment of the filter shown in FIG. 63 may be similar tothe embodiment shown in FIGS. 61 and 62 but may have a T-flow fittingarrangement. The inlet fitting 15 a, the outlet fitting 15 b, and thevent fitting 15 c may each be disposed in the head 163 of the capsulefilter 13 in a generally triangular pattern.

[0159] Filters embodying one or more aspects of the invention, includingcapsule filters having one or more of the axial fluid conduit, theradial passage, and/or the keying mechanism, have many advantages andrepresent a significant advance in the art. These features are even morevaluable when combined with the close fit between the housing and thefilter cartridge and the non-radial pleats of the filter cartridge. Forexample, the axial fluid conduit allows the fluid to sweep evenly alongthe axial length of the filter cartridge from the bottom to the top ofvice versa, reducing or eliminating dead zones at the bottom or top ofthe annular channel. The radial passage coupled to the lower channelsunder the lower end cap further enhances the even sweep and distributionof fluid flow under the filter cartridge and in the annular fluidchannel around the filter cartridge and further avoids dead zones at thebottom of the annular channel. The keying mechanism ensures that thefilter cartridge is centered in the filter cartridge chamber andprovides a uniform annular channel, even further enhancing the evendistribution of fluid flow around the filter cartridge. These advantagescombined with the low hold up volume provided by the close fit betweenthe housing and the filter cartridge and by the non-radial pleats of thefilter cartridge provide a filter with far superior performance thanconventional filters with respect to reducing hold up volume and deadzones, providing an even distribution of fluid flow upward, or downward,along the filter cartridge; sharpening rise time; and minimizing thetime to output a fluid which has a desired level of cleanliness and issubstantially free of gas bubbles.

EXAMPLE 1

[0160] A test system 300 shown in FIG. 64 is used to evaluate liquiddisplacement in a first filter, a second filter, and a third filter as adispense liquid is dispensed through the filters. The test system 300includes a dispense liquid container 301, a dispense pump 302, a housing303, a drawback 304, a container 305 on a balance or scale 306, andelectronics 307, such as a PC, coupled to the scale 306. The firstfilter, which is similar to the capsule filter 310 shown in FIG. 65 bututilizes the bowl 311 shown in FIG. 66, has a filtration area of 660 cm²and a hold up volume of 42. cc. The second filter, which is similar tothe capsule filter 312 shown in FIG. 67 but utilizes the bowl 313 shownin FIG. 68, also has a filtration area of 660 cm² and a hold up volumeof 42 cc. The third filter, which is similar to the capsule filter 314shown in FIG. 69, has a filtration area of 2800 cm² and a hold up volumeof 130 cc. The hold up volume of each filter is the inner volume of thefilter housing, including the bowl, minus the hardware volume of thefilter cartridge.

[0161] To monitor dispense weight, two kinds of liquids, which havedifferent specific gravities, are used:

[0162] (1) hexyleneglycol (s.g.=0.923 at 20 deg. C., vis.=34.4 m.Pas at20 deg. C., s.t.=27 mN/m at 20 deg. C.) and

[0163] (2) ethyleneglycol (s.g.=1.11 at 20 deg. C., vis=25.66 mPa.s at16 deg. C., st=46 mN/m at 20 deg. C.).

[0164] The dispense is carried out pulsationally rather thancontinuously, and the dispense cycle has a 6 sec. dispense time and a 12sec. wait time. The dispense weight for the hexyleneglycol isapproximately 3.05 g/shot and for the ethyleneglycol is approximately3.70 g/shot. The minimum range is 0.001 g.

[0165] The test procedure is as follows:

[0166] (1) a test filter is installed in the housing;

[0167] (2) hexyleneglycol is run through the filter and the housing isthen filled with liquid;

[0168] (3) ethyleneglycol is passed through the filter wetted by thehexyleneglycol;

[0169] (4) hexyleneglycol is displaced with ethyleneglycol;

[0170] (5) the weight of fluid filtered is measured as a function oftime during displacement;

[0171] (6) ethyleneglycol is displaced with hexyleneglycol; and

[0172] (7) the weight of fluid filtered is measured as a function oftime.

[0173] The raw data is presented in FIG. 70. The raw data is convertedinto W values as follows:

[0174] (1) displacement from hexyleneglycol to ethyleneglycolcorresponds to W=W1−W(n);

[0175] (2) displacement from ethyleneglycol to hexyleneglycolcorresponds to W′=W′(n′−W2;

[0176] (3) dispense weight corresponds to W(g); and

[0177] (4) shot number corresponds to n.

[0178]FIGS. 71 and 72 show that it takes 60 shots for the first filter310 and 140 shots for the third filter 314 until the dispense weightreaches a stable level. It takes 80 shots until the dispense weightreaches a stable level for the second filter 312.

[0179] In FIGS. 73-75, the areas enclosed by the x- and y-axes and thedata profiles indicate the total weight for the displacement. In FIGS.73 and 74, the profiles and values from hexyleneglycol to ethyleneglycoland from ethyleneglycol to hexyleneglycol were very close. In FIG. 75,the profiles were a bit further but the values were almost the same. Thedisplacement volume from ethyleneglycol to hexyleneglycol must be equalto that from hexyleneglycol to etyleneglycol in order to displace all ofthe liquid. Therefore, all of the filters allow most of the liquid to bedisplaced.

EXAMPLE 2

[0180] A test system 320 shown in FIG. 76 is used to determine bubbleand particle counts downstream of the first filter, second filter andthird filter of Example 1. The test system includes a source 321 of air,a pressure tank 322, a pressure guage 323, the test filter 324, aparticle counter 325 (e.g., a RION KS-16F), and a flow meter 326. Thetest liquid is the hexyleneglycol of Example 1.

[0181] The test procedure is as follows:

[0182] (1) the test liquid is loaded into the tubing and the testfilter;

[0183] (2) after venting, the liquid is passed through the test filterto the particle counter, which is started simultaneously just afterventing, and

[0184] (3) the bubble and particle counts for bubbles/particles greaterthan 0.1 and 0.2 micron were measured as a function of time at a 10mL/min flow rate.

[0185] As shown in FIG. 77, the first and second filters showed a quickdrop for the downstream particles. The first and second filters have asmaller filtration area than the third filter and contain less airinitially than the third filter. This difference in filtration area maybe the cause of the difference in the initial purge. The first andsecond filters, which are smaller than the third filter, more quicklyreduce the bubble/particle counts downstream of the filter. Thus, thefirst and second filters better reduce waste time and volume duringphotoresist dispense.

[0186] The present invention has been described in terms of severalembodiments. However, the invention is not limited to these embodiments.One or more of the features of one embodiment may be eliminated orcombined with one or more of the features of another embodiment withoutdeparting from the scope of the invention. Further, entirely differentembodiments may be envisioned, particularly in light of the foregoingteachings. Accordingly, the invention includes all variations andmodifications encompassed with the scope of the attached claims.

1. A filter comprising: a filter cartridge and a housing having at leastone fitting and defining a chamber, the filter cartridge being disposedin the chamber, wherein the housing includes a fluid conduit whichextends axially from the fitting along the periphery of the filtercartridge chamber, the fluid conduit being isolated from the filtercartridge chamber along a substantial portion of the length of the fluidconduit.
 2. The filter of claim 1 wherein the axially extending fluidconduit is isolated from the filter cartridge chamber for at least about70 percent of the length of the fluid conduit.
 3. The filter of anypreceding claim wherein the housing has a side wall and the axiallyextending fluid conduit is disposed in the side wall of the housing 4.The filter of any preceding claim wherein the axially extending fluidconduit extends from the fitting at the top of the filter to the bottomof the housing.
 5. The filter of any preceding claim wherein the fittingis an inlet fitting or an outlet fitting.
 6. The filter of any precedingclaim wherein the filter cartridge includes an end cap and wherein thehousing includes a wall adjacent to the end cap and a radial passagewhich extends along at lease one of the end cap of the filter cartridgeand the wall of the housing and fluidly communicates between the axiallyextending fluid conduit and the filter cartridge chamber.
 7. The filterof any preceding claim further comprising a keying mechanismcooperatively arranged with the housing and the filter cartridge tocenter the filter cartridge in the filter cartridge chamber.
 8. A filtercomprising: a filter cartridge having an end cap and a housing having atleast one fitting and defining a chamber, the filter cartridge beingdisposed in the chamber with the end cap of the filter cartridgeadjacent a wall of the housing, wherein the housing has a radial passageextending along at least one of the end cap of the filter cartridge anda wall of the housing and fluidly communicating between the fitting andthe filter cartridge chamber.
 9. The filter of claim 6 or 8 wherein theradial passage extends to the center of the filter cartridge and whereinthe housing includes flow channels between the end cap of the filtercartridge and the wall of the housing, the flow channels fluidlycommunicating between the radial passage and the annular channel betweenthe filter cartridge and the housing.
 10. The filter of any of claims 6,8 and 9 wherein the radial passage is isolated from the filter cartridgechamber over much of the length of the radial passage.
 11. The filter ofany of claims 8, 9 and 10 further comprising a keying mechanismcooperatively arranged with the housing and the filter cartridge tocenter the filter cartridge in the filter cartridge chamber.
 12. Afilter comprising: a filter cartridge; a housing defining a chamber, thefilter cartridge being disposed in the chamber; and a keying mechanismcooperatively arranged with the housing and the filter cartridge tocenter the filter cartridge in the filter cartridge chamber.
 13. Thefilter of any of claims 17, 11 and 12 wherein the keying mechanismcomprises mating shapes on the interior bottom wall of the housing andthe bottom of the filter cartridge.
 14. The filter of claim 13 whereinthe mating shapes are generally conical.
 15. A filter comprising: afilter cartridge including a filter element having non-radiallyextending pleats, the height of each pleat being greater than (D−d)/2and less than or equal to (D²−d²)/[4(d+2t)] where D and d are theoutside and inside diameters, respectively, of the pleated filterelement at the crests and roots of the pleats and t is the thickness ofa pleat leg, and a housing fitting around the filter cartridge andhaving an inlet and an outlet defining a fluid flow path, the filtercartridge being disposed in the housing in the fluid flow path and thehousing and the filter cartridge being arranged to reduce hold up volumeand dead zones in the fluid flow path.
 16. The filter of any precedingclaim wherein the annular channel between the filter cartridge and thehousing has an area on the order of the area of an inlet fitting or anoutlet fitting.
 17. The filter of any preceding claim wherein thehousing has an inclined bottom surface, thereby enhancing removal ofbubbles in the liquid from the filter.